Electrophotographic light-sensitive elements which have hitherto been used include those comprising an electrically conductive support having vapor-deposited or coated thereon as a light-sensitive layer Se, Se-Te alloy, or Se-As alloy, or an organic photoconductor such as PVK (polyvinyl carbazole)-TNF (2,4,7-trinitrofluorenone). However, when these known elements are repeatedly used, they tend to be damaged due to peeling of a transfer paper or cleaning of residual toner on the light-sensitive layer, or the light-sensitive layer tends to be worn away, and, therefore, the elements must be replaced with new ones within a relatively short period of time, before the electrophotographic characteristics are degraded. In order to overcome such defects, it has been known in the art that a protective layer can be provided on the surface of the light-sensitive element. One type of such protective layer is an electrically insulating surface layer composed of a highly electrically insulating material. Such an electrically insulating surface layer has advantages such as that the thickness can be increased and that those having high mechanical strength can be chosen. However, in order to repeatedly use a light-sensitive element with this type of protective layer, a specific latent image-formation process, (for example; (A) a first charging, a second charging with an opposite polarity to that of the first charging, and imagewise exposure; or (B) a first charging, a second charging with opposite polarity while simultaneous imagewise exposing, and uniform exposure) is required. Furthermore, such a process requires two or more charging steps in one copying operation, and thus the apparatus to be used is necessarily complicated. This may result in electrophotographic characteristics that are instable, and the cost is high. Another type of protective layer is a surface layer useful in the so-called Carlson process, which does not require the above-described specific latent image-formation process, and in which a simple operation of charging and imagewise exposure is carried out. The protective layer should be rendered less electrically insulative to prevent accumulation of charges into its surface or interior. A method which has hitherto been employed for this purpose is to add a quaternary ammonium salt or the like to the protective layer. Such materials generally greatly change in conductivity by moisture absorption, and the conductivity of the protective layer reduces when drying, whereby charges accumulate and result in fogging of the image. Further, in high moisture conditions, the conductivity excessively increases, and transfer of the charges in a longitudinal direction takes place, whereby fading of the image tends to occur. In addition, the conventional protective layer must be relatively thin, to the extent of several microns or less, for purposes of use in the Carlson process. Such protective layers are hardly satisfactory in mechanical strength, and are colored by substances added for the purpose of lowering the electrical insulation properties, and thus undesirable influences on the spectral sensitivity of the light-sensitive element occur.
An attempt to control the conductivity of the protective layer has been made, in which an electrically conductive powder is dispersed in a binder resin as described, for example, Japanese Patent Application (OPI) No. 3338/1978. In this case, when carbon or a metal is dispersed, light absorption is strong, and therefore, it is difficult to increase the conductivity while maintaining the transparency.